I just spun up a new production org and I am getting the following error when trying to send a POST request to my REST endpoint.

Nested object for polymorphic foreign key must have an attributes field before any other fields.

POST Request

   "account": {
      "name": "test"

Apex Class

global without sharing class LeadImportRequestHandler {

    global class ResponseMessage {
        public Boolean isSuccess;
        public String message;

    global static ResponseMessage doPost() {
        ResponseMessage response = new ResponseMessage();
        RestRequest req = new RestRequest();
        RestResponse restRes = new RestResponse();
        Account account = new Account();

        try {            
            String body = RestContext.request.requestBody.toString();
            account = (Account)JSON.deserialize(body, sObject.class);
            req = RestContext.request;
            restRes = RestContext.response;
            insert account;
        } catch (Exception e) {
            restRes.statusCode = 400;
            response.isSuccess = false;
            response.message = e.getMessage();
        return response;

The class throws the error on the following line of code account = (Account)JSON.deserialize(body, sObject.class);

I know sending the below request solves the issue but for other Salesforce orgs I have worked on I simply sent the first request and it worked fine. The difference between the new org is the apex class is not associated with a Sites page where classes on the previous orgs are. Any ideas or suggestions would be appreciated. Thanks!

Working Request

    "attributes": {
        "type": "Account"
    "name": "test"
  • try to change sObject.class to account.class – Ilya Lepesh Jul 14 '16 at 17:32
  • off topic, but why don't you just do restRes.statusCode = response.getStatusCode(); – EricSSH Jul 14 '16 at 17:59
  • @EricSSH the getStatusCode() method is an HttpResponse class method. So this wouldn't work in this situation since I am using my own wrapper class, ResponseMessage. – Gabe Wonders Jul 18 '16 at 17:01

According to the JSON documentation:

Object deserialize(String jsonString, System.Type apexType)

Deserializes the specified JSON string into an Apex object of the specified type.

You can use sObject with attributes, or specify exact class type:

string body = '{"account":{"name":"test"}}';
Account acc = (Account)JSON.deserialize(body, Account.class);

USER_DEBUG [3]|DEBUG|Account:{Name=test}
| improve this answer | |
  • How would one deserialize this in JS instead of Apex code? I'm using JSForce and running into this same error, but I don't have access to the Account.class object – Big Money May 15 '19 at 16:57

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